sha1_name: support @{-N} syntax in get_sha1()

diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index 2921da320d2b84df4d15ec2745e6d94093dd6907..3ccef2f2b3295c6d5e14b8f3a9d354d7b57598da 100644 (file)
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -212,6 +212,9 @@ when you run 'git-merge'.
   reflog of the current branch. For example, if you are on the
   branch 'blabla', then '@\{1\}' means the same as 'blabla@\{1\}'.
 
+* The special construct '@\{-<n>\}' means the <n>th branch checked out
+  before the current one.
+
 * A suffix '{caret}' to a revision parameter means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
   'rev{caret}'